The electron displacement effect observed in the given structures is known as

Explain the delocalization of electrons in $CH_3-CH_2^+$ and $CH_3-CH=CH_2$.

What is the electromeric effect?

Explain why alkyl groups act as electron donors when attached to a $\pi$ system.

Which acid of each pair shown here would you expect to be stronger?
$(i)$ $CH_3CO_2H$ or $CH_2FCO_2H$
$(ii)$ $CH_2FCO_2H$ or $CH_2ClCO_2H$
$(iii)$ $CH_2FCH_2CH_2CO_2H$ or $CH_3CHFCH_2CO_2H$
$(iv)$ $F_3C-C_6H_4-COOH$ or $H_3C-C_6H_4-COOH$

The $+I$ effect of alkyl groups is in the order: